How can I convert from a double ** to a const double**
I am using ROOT and with a deconvolution function. When running, I receive an error:
cannot initialize a parameter of type 'const Double_t **' (aka 'const double **') with an lvalue of type 'Double_t **'(aka 'double **')
I define the parameter as such:
Double_t ** resp = new Double_t * [ybins]; for (int f = 0; f < xbins ; f = f+1){ for (int i = 0; i < ybins; i = i+1){ resp[f][i] = hinr->GetBinContent(i+1,f+1); } } Note: the answer to the "duplicate" question explains why the implicit cast does not work but it doesn't answer this question, "How do I do what I need to do?" That answer is:
Use either a c style cast or a c++ style const_cast. The c++ const_cast is preferred because it makes your intent more clear.
#include <iostream> int main(int argc, char * argv[]) { double a = 3.14159; double * b = & a; double **c = & b; const double ** d = (const double **) c; std::cout << **d << std::endl; // const_cast is the preferred approach. const double ** e = const_cast<const double **> (c); std::cout << **e << std::endl; return 0; } 
respofybinsdouble*which are not initialised (resp[f]can be anything, but certainly does it not point to an array ofdoubles); then you assign toresp[f][i].constin the code snippet you have given us, so how did you get that error?